Police are appealing for witnesses and information following an assault in Watford.
The incident occurred at around 5.50pm on Sunday 4 June, on the 321 bus as it headed towards Rickmansworth.
It is reported that an altercation occurred between a man and a woman. During the altercation, the woman sustained a serious injury to her shoulder and bruising to her arm.
The man then reportedly left the bus on St Albans Road, close to the junction with Salisbury Road.
Detective Sergeant Sarah Hern, who is investigating, said: “We are appealing for witnesses and information as part of our continued enquiries.
“The bus was carrying several passengers at the time of this incident, several of whom tried to intervene. I am asking these people to please contact us as you may have vital information that could progress our investigation.”